Hello, friend!
Voice services, including POTS, fax, modem, ISDN, and R2 services, apply to multiservice access node (MSAN), fiber to the building (FTTB), fiber to the curb (FTTC), fiber to the home (FTTH), fiber to the office (FTTO), and enterprise private line scenarios.

You can refer to the MA5600 product documentation. For details, see:
Voice Service Networking Applications
Thanks!